1. Field of the Invention
The technical field relates to a touch panel which is used, as one example, to operate various electronic apparatuses.
2. Background Art
With their increased functionality and diversity in recent years, many electronic apparatuses such as mobile telephones and electronic cameras have been provided with a light-transmitting touch panel. Such a touch panel is installed on the front surface of a liquid crystal display or other display device in these electronic apparatuses. The touch panel allows the user to switch between various functions by touching the panel with a finger, pen or other pointing device while watching the display of the display device through the panel. There is a demand to make such touch panels less costly and more user-friendly.
FIG. 7 is a sectional view of a conventional touch panel, and FIG. 8 is an exploded perspective view of the touch panel. Note that the dimensions of some parts in these drawings are enlarged for clarity. The touch panel includes upper substrate 1 having upper conductive layer 3 on its bottom surface, and lower substrate 2 having lower conductive layer 4 on its top surface. Upper substrate 1 may be made of a light-transmitting film, and lower substrate 2 may be made of light-transmitting glass. Upper conductive layer 3 and lower conductive layer 4 may be made of indium tin oxide, which has light-transmitting characteristics.
Upper substrate 1 has a pair of upper electrodes 5A and 5B, along opposing first and second sides of upper conductive layer 3. Upper electrodes 5A and 5B may be made of silver. Lower conductive layer 4 has third and fourth sides which are orthogonal to the first and second sides of upper conductive layer 3. Lower substrate 2 includes a pair of lower electrodes 6A and 6B along the third and fourth sides. The ends of upper electrodes 5A and 5B extend to the center of the front side of upper substrate 1. The ends of lower electrodes 6A and 6B extend to the center of the front side of lower substrate 2.
Lower conductive layer 4 has dot spacers (not shown) on its top surface. The dot spacers are made of insulating resin, and are arranged with a predetermined space from each other. The touch panel further includes frame-like insulating layers 7 and 8. Insulating layer 7 is formed along the outer periphery of the bottom surface of upper substrate 1, and insulating layer 8 is formed along the outer periphery of the top surface of lower substrate 2. Upper substrate 1 and lower substrate 2 are pasted together along their outer peripheries with adhesive 9 such that upper conductive layer 3 and lower conductive layer 4 face each other with a predetermined space. Adhesive 9 is applied to the bottom surface of insulating layer 7 or the top surface of insulating layer 8.
The touch panel further includes light-transmitting film-like display sheet 10. Display sheet 10 has light-transmitting hard coat layer 10A on its entire top surface. Hard coat layer 10A may be made of acrylic. Display sheet 10 also has light-transmitting part 10B at its center, frame-like decoration part 10C along its outer periphery, and adhesive layer 10D on the bottom surface of decoration part 10C. Decoration part 10C is painted a dark color such as black or gray. Display sheet 10 is pasted on the top surface of upper substrate 1 with adhesive layer 10D.
The touch panel having this structure is installed on the front surface of a liquid crystal display or other display device (not shown), and mounted on an electronic apparatus. The ends of upper electrodes 5A, 5B and the ends lower electrodes 6A, 6B of the touch panel are electrically connected to an electronic circuit (not shown) of the apparatus via, for example, a wiring board or a connector (not shown).
The user touches the top surface of upper substrate 1 to select a desired menu with a finger, pen, or other pointing device while watching the display of the display device disposed on the rear surface of the touch panel through light-transmitting part 10B of display sheet 10. In this case, upper substrate 1 is bent such that the touched part of upper conductive layer 3 comes into contact with lower conductive layer 4.
The electronic circuit sequentially applies voltages across upper electrodes 5A and 5B and across lower electrodes 6A and 6B. The electronic circuit then detects the touched part from the ratio between the sides of upper conductive layer 3 and the sides of lower conductive layer 4 which are orthogonal to upper conductive layer 3. This allows the user to switch between various functions of the apparatus, thereby selecting a desired menu from multiple menus.
It, however, takes time to manufacture the conventional touch panel because of the large number of components. As described above, upper substrate 1 having upper conductive layer 3 and insulating layer 7 on its bottom surface is pasted together with lower substrate 2 having lower conductive layer 4 and insulating layer 8 on its top surface via adhesive 9. In addition, display sheet 10 having hard coat layer 10A and decoration part 10C is pasted on the top surface of upper substrate 1 via adhesive layer 10D.